Txflier

You just have to find what works for you. I jump with some incredible freefier's and have pretty much gotten the same advice, but what works for some may not work for others. The advice I got was, all paraphrased... push heels down and out, this will help with getting your legs where they need to be,(this helped me because I seemed to keep my feet tucked under my ass), I also had a tendency to get the leg out signal in AFF A LOT, if your arms are straight and back your chest will be pushed forward, try it on the couch... The majority of FF I've talked to say arms should be at 90, which seems hard to do even for the people that say do that. back straight if not slightly arched back, so you don't backslide. and of course never cork out, go to back flying if you are unstable. While I don't consider myself an expert in any means, I think I progressed pretty quickly with the help of many great fliers. try and get some video to see what makes you unstable... I know you want a straight--- Ok arch and push your hips out answer, but FF'ing is more difficult than that. Stick with it and there will be one jump that it just all of a sudden clicks, and you'll say, Why the hell didn't I get that right away... Good luck.

To be continued, time to finish my movie and crash.

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>They don't skim, they protect the work and property rights.

They protect someone else's work from other lawyers.

Some IP lawyers seem little better than mobsters. "Hey, you wanna pay us some, uh, protection money, on a per-hour basis? You do that I'll make sure my lawyer pal Thurston over there don't have a little accident with your patent."

>I wouldn't call that skimming I'd call that good business.

Well, so is "protection."

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Maybe shoot a message to Bill Booth and see if he was glad he had "protection" on his 3 ring.

I'm not the rope totin charlie Bronson wanna be that's getting us fucking lost.

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>They don't skim, they protect the work and property rights.

They protect someone else's work from other lawyers.

Some IP lawyers seem little better than mobsters. "Hey, you wanna pay us some, uh, protection money, on a per-hour basis? You do that I'll make sure my lawyer pal Thurston over there don't have a little accident with your patent."

>I wouldn't call that skimming I'd call that good business.

Well, so is "protection."

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They protect it from reverse engineering and theft of the idea from other less talented engineers that try and steal the idea...

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>They don't skim, they protect the work and property rights.

They protect someone else's work from other lawyers.

Some IP lawyers seem little better than mobsters. "Hey, you wanna pay us some, uh, protection money, on a per-hour basis? You do that I'll make sure my lawyer pal Thurston over there don't have a little accident with your patent."

>I wouldn't call that skimming I'd call that good business.

Well, so is "protection."

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hahaha look at any country that doesn't have IP law and you have all sorts of knock off's and fakes. So a engineer that creates something should have no protection from some half ass jerk off that reverse engineers his hard work and sells it for half the price because he can make some 12 yo build the product??? the IP laws are there to protect the creators from someone and coming in and stealing what they rightfully made. Per the Laws of the US. and it's not that hard to get a patent, if the engineer is smart enough to build something, then he should be smart enough to put the paper work through, but most engineers don't want to read, they want to build. So I guess there should be nobody to uphold the law... Fuck the lawyers and the judges.. Let's have good ol fashion lynchings if someone steals my idea. Trust me I'm not a fan of criminal law I've had my fair share of expenses, but I think IP law is something worth while.. But hey I'm sure an engineer such as myself would love to have somebody sell a product I created for half the price... Ok stepping off of the soap box and making another drink....

I'm not the rope totin charlie Bronson wanna be that's getting us fucking lost.

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We have way too many MBAs. Just as we have too many lawyers. Neither group creates wealth, they just manipulate and skim off the top.

Not True! Intellectual Property Attorneys, Which you pretty much need an engineering or biology degree for help protect the inventions of companies which in turn helps companies keep and generate consumer goods and wealth!

You just gave a great example for his argument

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how so Squeak, The lawyers are engineers themselves, helping protect the inventions, and many have patents themselves... They don't skim, they protect the work and property rights. I wouldn't call that skimming I'd call that good business.

I'm not the rope totin charlie Bronson wanna be that's getting us fucking lost.

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As for the population? How to get them interested in the field? Pay more! Much MUCH MUCH MORE! Make it such that the pay of a base engineer is equal to that on an MBA.

While engineers working for the government in New Jersey don't too too well, looking at national averages they do better than MBAs. Average salaries off indeed.com show

$81K for an MBA
$93K for a software engineer with $99K for senior engineers
$86K for an electrical engineer with $98K for senior engineers
$82K for a mechanical engineer with $93K for senior engineers

We have way too many MBAs. Just as we have too many lawyers. Neither group creates wealth, they just manipulate and skim off the top.

How bout right here. 34 yo Caucasian male recent ME Grad. Anybody looking for an Engineer.

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This was definitely rare. I can only remember seeing one or two dead bears by the road over the years.
Moose and deer on the other hand are common. By the way, do ya know the main difference between a moose and a deer?,,deer are stupid, moose just don't give shit.

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I thought it was Honey Badger don't give a shit.
http://www.youtube.com/watch?v=4r7wHMg5Yjg

I'm not the rope totin charlie Bronson wanna be that's getting us fucking lost.

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My internet is too slow to look but it was on facebook when I saw it, damn funny!!!

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I know and I can't find the damn thing anywhere.. Come on people you are all useless.

I'm not the rope totin charlie Bronson wanna be that's getting us fucking lost.

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I think it's more subjective than a simple jump number. I've been told more than a few times that it's detrimental to abandon belly flight too soon. There are jumpers with 200+ jumps that can't work well in RW because they didn't learn basic skills.

I have heard that too, but I don't buy it. As long as your survival belly skills are solid (ie. track and pull stable) I don;t see why you should have to wait to learn to sit fly. Just be aware that freeflying in groups is more dangerous than belly, so you should limit your FF to small groups (three or less) until you are solid and do not cork out.

easier to fly on your back if you can fly on your belly....if you can figure out your belly flight, it will give you a good idea of how the air works and make it easier for you to balance, as well as its how you learn, you should have more situation awareness on your belly before moving onto a faster part of the jumping where many many people have forgot to pull and had a cypress fire or burned in. belly keeps it safe for a while.....

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I started learning FF at jump 46 I had done my SCR around 36 and felt comfortable on my belly. I think if FF is you want to do and you are proficient on your belly go for it. I'd recommend getting comfortable on your back so you don't cork out. and as far as group size I'd definitely keep to 2 or three ways with good fliers that can get out or your way if need be.. Good luck on the FF'ing. Do some tunnel if you can.

I'm not the rope totin charlie Bronson wanna be that's getting us fucking lost.

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You are getting close. You do have to set it up as second order. You absolutely must have the acceleration equations. That is how your forces are going to get factored in. As you have it now, you have forces in your velocity equations. Not where they are supposed to be. Also, your initial conditions are a mix of a velocity (85) and an acceleration (9.81), and it looks like these should both be velocities.

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I think your right.. I think my initial condition in the Z direction would start at 0 and in the x direction should be the speed of the plane.

I'm not the rope totin charlie Bronson wanna be that's getting us fucking lost.

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Oh, and your initial vector, y0, in your main file is [0 85 (convert to proper units) 0 0]

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Hey all, I'm doing a project for Dynamic systems of modeling. I'm trying to plot the distance a jumper will be away from the plane after exit at a given time using matlab or similar program.

Assumptions: Plane Velocity 100 mph
Altitude 13.5 K
gravity 32.2 (m/s^2)

I've come up with a few equations.
Y(t) = -.5 *g * t^2 +Vo*t + Yo

Y(t)=altitude wrt to time
g-gravity
t-time
Vo initial velocity
Yo-initial altitude

But this is just assuming the objects initial velocity is 0 which isn't true.. So delving a little deeper. using drag coefficient

m * dv/dt = .5 * rho *Cd * A * V^2 -m*g

rho- density of air at 13.5k
Cd- drag coefficient
A - surface area
V- Velocity
m-mass
g-gravity.

but my goal is not to find terminal velocity or velocity wrt to time. I want to find distance away from plane after x seconds.

If you got any ideas I'd appreciate it. I'm trying to get this project done so I can study for finals on Mon.

It's actually quite tricky problem because the v^2 in the drag term results in the x and y distances being coupled instead of independent.

You can check your results against mine:

http://mypages.iit.edu/~kallend/skydive

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I think you need to add a little complexity to capture at least some of the dynamics of this problem. Since I really should get back to work, I'll just give you my initial impressions.

First, set this up as a vector problem. It doesn't necessarily need to be 3-dimension. You can assume no lateral motion and limit motion to the xz-plane (horizontal and vertical motion). This will allow you to quantify the velocity as a vector as well. Initial horizontal velocity is 100 mph, initial vertical velocity is 0 mph. The direction of the drag vector is directly related to velocity. It's in the opposite direction.

Second, start from the beginning to derive your equations of motion. Begin with the jumper's position in the xz space. You can set the (0,0) point as the exit point. Next take the derivative to get the velocity equation, and take the derivative again to get the acceleration equation. Depending on how you define everything, as in if you have a local coordinate system for your jumper, you may need to use the Transport Theorem to to make the derivatives work right. Use F=ma to get your equation of motion.

Third, once you get these derived, there are several equations you need to input into Matlab. In the xz coordinate system, you would need the dx/dt, d(dx/dt)/dt, dz/dt, and d(dz/dt)/dt with all the forces and whatnot included. Put these in an m-file, set up a driver m-file, and use ode45 to solve the system of equations. It will output x, dx/dt, z, and dz/dt. This will tell you your final position in xz space, and you can do a quick calculation to determine where the plane is if it stayed at its original speed and direction. From there you can get the final distance they are from each other.

Hope this helps. It seems like a fun problem. If I had more time (i.e., not at work), I'd derive it and give you some more concrete pointers.

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This is exactly what I'm looking to do.
main
n=2;
x0=zeros(n,1);
Vx(0)=85;
Vz(0)=9.81;

Tinit=0;
Tfinal=55;
Tspan=[Tinit,Tfinal];
[t,x]=ode45(@Johns9_25_equations,Tspan,V0);
plot(t,V(:,1),t,V(:,2))

grid
xlabel('time(s)')
ylabel('Response')


M function file
function Dx =Johns9_25_equations(t,x)
Dx=zeros(2,1);

rho=0.82; %(kg/m^3)
Cd=0.668402;
A= 0.9968; %(m^2)
Vxp= 44.7; %(m/s)
g= 9.81; %(m/s^2)

Vx(1)= Cd*rho*A*Vxp^2/(M*2);
Vz(2)= g;

I'm not the rope totin charlie Bronson wanna be that's getting us fucking lost.